The goal of this study is to explore, through the use of an intensive case study methodology, drug-abusing and non-drug-abusing responses to traumatic stress. The specific aims are four-fold: 1) To identify the key psychodynamic and social-structural characteristics (pre- and post-trauma) which are related to both "vulnerability" and "invulnerability" regarding drug abuse as a response to traumatic stress; 2) to relate the individual's response (whether drug-abusing or non-drug-abusing) to his perception of the traumatic experience, or, in other words, to the "meanings" of the experience for the individual; 3) to explore the relationship between the individual's response to the traumatic experience (whether drug-abusing or non-drug-abusing) and the development of a posttraumatic stress disorder, clinically defined by DSM III; and 4) to identify the specific functions of drug abuse as a response to traumatic stress. The stressor under study is exposure to heavy combat in the Vietnam war. Using the representative case method, 20 Vietnam combat veterans with no drug history prior to combat will be selected, equally divided into two categories: those having serious, prolonged drug abuse problems in the postcombat period, and those showing clinical symptoms of a posttraumatic stress disorder but having no significant drug use. A third group of 10 veterans who appear to have been "invulnerable" to both drug abuse and the posttraumatic stress disorder following their combat experience will also be purposely selected. Data collection techniques include written questionnaires, semi-structured interviews, and unstructured psychodynamic interviews. Resulting data will be integrated into 30 individual case summaries. Using this data base, separate analyses will be conducted to identify the patterns and trends within and between the three sample groups atic stress, and the relationship between these two disorders. The long-term objectives of the study are to provide an empirical basis for developing appropriate therapeutic strategies for the clinical treatment of drug-related problems which may be part of given individuals' responses to traumatic stress, as well as strategies for preventing drug-abusing responses to trauma.